net: enetc: fix build warning when PAGE_SIZE is greater than 128K

The max buffer size of ENETC RX BD is 0xFFFF bytes, so if the PAGE_SIZE
is greater than 128K, ENETC_RXB_DMA_SIZE and ENETC_RXB_DMA_SIZE_XDP will
be greater than 0xFFFF, thus causing a build warning.

This will not cause any practical issues because ENETC is currently only
used on the ARM64 platform, and the max PAGE_SIZE is 64K. So this patch
is only for fixing the build warning that occurs when compiling ENETC
drivers for other platforms.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601050637.kHEKKOG7-lkp@intel.com/
Fixes: e59bc32 ("net: enetc: correct the value of ENETC_RXB_TRUESIZE")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260107091204.1980222-1-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: WeiFang-NXP

drivers/net/ethernet/freescale/enetc/enetc.h

@@ -79,9 +79,9 @@ struct enetc_lso_t {
 #define ENETC_RXB_TRUESIZE	(PAGE_SIZE >> 1)
 #define ENETC_RXB_PAD		NET_SKB_PAD /* add extra space if needed */
 #define ENETC_RXB_DMA_SIZE	\
-	(SKB_WITH_OVERHEAD(ENETC_RXB_TRUESIZE) - ENETC_RXB_PAD)
+	min(SKB_WITH_OVERHEAD(ENETC_RXB_TRUESIZE) - ENETC_RXB_PAD, 0xffff)
 #define ENETC_RXB_DMA_SIZE_XDP	\
-	(SKB_WITH_OVERHEAD(ENETC_RXB_TRUESIZE) - XDP_PACKET_HEADROOM)
+	min(SKB_WITH_OVERHEAD(ENETC_RXB_TRUESIZE) - XDP_PACKET_HEADROOM, 0xffff)
 
 struct enetc_rx_swbd {
 	dma_addr_t dma;